1. Field of the Invention
The invention relates to environmental testing systems, and more particularly, to environmental testing systems capable of exposing a test piece to sand and dust.
2. Description of Related Art
Many pieces of equipment are subjected to environmental extremes during their service lifetimes. Those environmental extremes may be, for example, extremes of temperature, pressure, vibration, acceleration, or shock. Equipment may also be subjected to environmental conditions such as rain, wind, sand, dust, and humidity, to name a few. These environmental conditions can shorten the operational lifetime of a piece of equipment or cause it to fail entirely.
Over time, various methods have evolved for testing equipment to determine whether it can withstand various environmental extremes and conditions, and if so, what effect those extremes might have on the equipment. Most of these methods involve placing the equipment in question in an environmental test chamber that is equipped to simulate the desired environmental extremes.
Environmental testing techniques and methods are used widely in industry, both to certify that equipment will not fail under particular conditions and to evaluate the nature and reproducibility of failures that do occur. However, because resistance to environmental extremes is particularly important in the case of military equipment, a number of military organizations have produced standards documents that define how different types of environmental tests are to be performed. In the United States, MIL-STD-810G, “Department of Defense Test Method Standard for Environmental Engineering Considerations and Laboratory Tests” contains military standards for a variety of different types of environmental testing. Among the methods covered by MIL-STD-810G are methods for sand and dust environmental testing.
In a typical sand or dust environmental test, a piece of equipment is placed in a test chamber, and the test chamber is heated to an elevated temperature, e.g. 180° F. (82° C.). Either sand or dust is blown into the chamber continuously for the duration of the test, which typically lasts about 90 minutes.
Test systems for performing sand or dust environmental testing do exist, but these systems do have a number of difficulties. First and foremost, these systems can have difficulty producing a laminar airflow into the environmental testing chamber that has an even distribution of dust or sand particles, all of which are moving at essentially the same velocity. Moreover, in some of these systems, the air mover or blower that creates the airflow into the test chamber is directly exposed to the sand or dust, which can cause wear and reduce the effectiveness of the blower.
Finally, sand and dust may be hazardous to human health. Sand in particular can cause silicosis, a serious lung condition, if it is inhaled. For that reason, it is important to protect the operator of a sand and dust environmental testing system from exposure to the sand and dust.